The Core will identify and recruit patients and normal control subjects suitable for the human studies. It will characterize the research subjects with standardized diagnostic instruments, symptom rating scales, and neuropsychological tests. It will provide saliva samples for cortisol measures. It will perform structural and functional brain image acquisition with magnetic resonance imaging and positron emission tomography. It will perform functional image processing and statistical analyses with dedicated computer hardware and specialized software. It will provide treatment to patient subjects according to standardized protocols. The Core will also provide multidisciplinary expertise in neuropsychiatry, human behavioral neuroanatomy, and functional neuroimaging methodology and study design. This core will serve Project 1 (functional imaging of normal humans), Project 2 (functional imaging of patients with pathological fear), and Project 4 (structural imaging of hippocampus in normal humans and patients).